In making electrical connections between external circuitry and switch contacts on layers of a flexible switch, it is desirable to make internal electrical connections between spaced-apart layers of the switch. In an X-Y matrix flexible switch, for example, wherein there are rows of interconnected contacts on one layer and columns of interconnected contacts on a second spaced-apart layer, it is advantageous to bring out leads only from one of the layers, and make internal connections to the other layer by means contained within the switch. Conventionally, this has been done in several ways, each having its disadvantages.
DuRocher U.S. Pat. No. 3,879,586 shows inserting oversize plugs of elastomeric material with pressure-sensitive conductivity in holes in the spacer layer between two contact-carrying layers, and permanently compressing the plugs between one rigid and one stiff layer, so as to make the plugs conductive. Seeger et al. U.S. Pat. No. 3,789,167 shows using metal pins that protrude through the spacer layer and contact conductive plastic regions beneath the upper layer. Others, including Zurcher U.S. Pat. No. 4,028,509, make the internal connections with leads bent around a fold connecting the two layers.